1. Field of the Invention
The present invention relates to a method and apparatus for molding a flip chip semiconductor device and, more particularly, to a method for effectively molding a flip chip semiconductor device without generating a void and the mold apparatus for utilizing the method.
2. Description of Related Art
Conventionally, as shown in FIG. 9, a chip (70) is mounted on a substrate (71) to form a semiconductor device. The chip (70) is usually provided with a plurality of solder balls (701) formed on a surface thereof and arranged in a matrix form. As such, when in a chip mounting process, a well known flip chip mounting technique is employed to connect the solder balls (701) to corresponding connection points (711) on the substrate (71). Upper and lower surfaces of the substrate (71) are provided with connection points (711, 712), and the upper connection points (711) are electrically connected the corresponding lower connection points (712) via conductor lines inside the substrate (71). The lower connection points (712) are generally bonded with solder balls (not shown) for connecting to other circuit devices.
After such a chip mounting process, the next process to package a semiconductor device is known as an encapsulation process which may be carried out by well known underfill or molding techniques, both of which have the objective of trying to fill a space between the chip (70) and the substrate (71) with an encapsulant, in order to enhance the bonding strength of the solder balls (701). However, because the space between the chip (70) and the substrate (71) is so small and there are lots of solder balls (701) disposed therein, it is always particularly difficult for the encapsulant material to flow through and fill into the space.
Some recent inventions have tried to improve the flip chip encapsulation process.
U.S. Pat. No. 5,385,869 granted to Liu et al. for a xe2x80x9cSemiconductor Chip Bonded to a Substrate and Method of Makingxe2x80x9d teaches injecting encapsulation material into a mold apparatus to encapsulate a semiconductor chip. The semiconductor chip is mounted on a substrate which has a through hole defined therein, such that the injected encapsulation material can flow to the space beneath the chip more easily. However, because the mold apparatus provides a substantially hermetic inner space to hold the chip, the flowing speed of the encapsulation material in such a hermetic space can not be significantly improved. Moreover, undesired air in the mold apparatus is hard to escape during the encapsulation process, and thus voids are generated in the formed encapsulant, which results in a low productivity.
U.S. Pat. No. 5,866,442 granted to Brand for a xe2x80x9cMethod and Apparatus for Filling a Gap between Spaced Layers of a Semiconductorxe2x80x9d discloses using an apparatus having a pressure chamber and a vacuum chamber to carry out the encapsulation process. The semiconductor device to be encapsulated has a plurality of thermal vias defined in the substrate thereof and is positioned between the pressure chamber and vacuum chamber. In the encapsulation process, encapsulation material is injected into the pressure chamber and, at the same time, the pressure of the pressure chamber is increased while the air in the vacuum chamber is evacuated. Therefore, the pressure in the pressure chamber is applied to the vacuum chamber through the thermal vias, and thus the encapsulation material will quickly flow between the chip and substrate of the semiconductor device. However, because the aforementioned apparatus is especially designed for such an encapsulation process, the semiconductor packaging process may be negatively affected by employing such an apparatus. Furthermore, only one semiconductor device can be processed by the apparatus at a time, which severely influences the overall productivity of the semiconductor device. Therefore, there is a continuing need for the aforementioned method and apparatus to be improved.
One object of the present invention is to provide a method for effectively molding a flip chip semiconductor device without generating a void.
Another object of the present invention is to provide an apparatus for effectively molding a flip chip semiconductor device thereby increasing the productivity of the semiconductor device.
In accordance with one aspect of the present invention, a method for molding a flip chip semiconductor device is present, which includes the following steps: (A) providing a substrate having at least one air hole; (B) mounting a chip on the substrate by multiple solder balls such that the air hole is beneath the chip and surrounded by the multiple solder balls; and (C) placing the substrate mounted with the chip in a mold apparatus which defines at least one air channel aligning with the air hole, such that air can be exhausted via the air hole and the air channel when encapsulation material is entering the mold apparatus.
In accordance with another aspect of the present invention, an apparatus for molding a flip chip semiconductor device is present, which includes: an upper mold body defining a mold gate and an escape hole; and a lower mold body defining a plurality of air channels, each air channel being of a non-straight shape and having an end to face to an air hole defined in a substrate disposed between the upper mold body and the lower mold body.
Other objects, advantages, and novel features of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings.